A Software Defined Network (SDN) separates a control plane and a data plane and centers the control plane on a single controller so that the data plane manages simple traffic forwarding and the central controller determines where and how the traffic is transmitted to. In particular, by means of various Application Program Interfaces (APIs) provided via a northbound API and programming using them, the controller can perform various traffic controls based on network information. An OpenFlow protocol supports the SDN. According to the OpenFlow, the forwarding information is forwarded between the controller and a switch, and switch status or traffic information is forwarded to the controller.
The OpenFlow protocol for the SDN technology is being standardized and defines only a method for forwarding the traffic. Accordingly, it is not clear that the OpenFlow can gain any benefit by itself. Currently, the OpenFlow protocol is applied mostly to the switch which interconnects servers in a data center, and how to apply the OpenFlow to recent communication networks such as Long Term Evolution (LTE) network is not fully discussed. Hence, a method for properly applying the SDN is required.